Electromagnet and hydraulic valve comprising such an electromagnet

ABSTRACT

A solenoid valve ( 50 ) has a valve housing ( 51 ) with a valve slide ( 53 ) in which two magnets, with one pole ( 1 ) each, are inserted. The poles ( 1 ) each have a coil core ( 8, 9 ) which extends along a longitudinal axis ( 10 ) and in which in each case one armature tappet ( 17 ), which activates one end of the valve slide ( 53 ) with an activation end ( 27 ), is provided. Arranged on each armature tappet ( 17 ) is a magnet armature ( 23 ) which has two armature side faces ( 24, 25 ) which extend obliquely with respect to the longitudinal axis ( 10 ). The coil core ( 8, 9 ) has two core side faces ( 12, 19 ) which extend parallel to one armature side face ( 24, 25 ) in each case.

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a pole for a magnet which can be used inparticular in a hydraulic solenoid valve. The invention also relates toa magnet and to a hydraulic solenoid valve.

The poles known from the prior art have the disadvantage of a highdegree of inertia. For this reason, in particular hydraulic solenoidvalves are complicated to activate. Furthermore, the poles known in theprior art have a high degree of friction. Furthermore, when mounting itis necessary to take care that there are no air bubbles in the interiorof the armature space because the poles known from the prior art have amodified dynamic depending on the proportion of air in the armaturespace.

Furthermore, the poles known from the prior art have the disadvantage ofmarked wear.

SUMMARY OF THE INVENTION

The object of the invention is therefore to provide a pole which has alow degree of wear and is highly responsive. The pole which is to beprovided is to be insensitive to proportions of air in the armaturespace and to be of simple design. It is also the object of the inventionto provide a magnet which is improved in this respect and a hydraulicsolenoid valve which is improved in this respect.

This object is achieved by means of the subject matter of theindependent claims. Advantageous refinements emerge from the respectivesubclaims.

With such a configuration, the magnet armature moves transversely withrespect to the longitudinal axis when current flows through theelectrical coil. Because of the particular interrupted construction ofthe coil core in the region of the magnet armature, the magnetic fieldlines emerge, in fact, from a first coil core section, into the magnetarmature and out again and then into a second coil core section. Owingto the armature side faces which are of “oblique” construction withrespect to the longitudinal axis, a force component which extendstransversely with respect to the longitudinal axis and acts on themagnet armature is produced, said force component displacing the magnetarmature, and thus the armature tappet connected to the magnet armature,transversely with respect to the longitudinal axis. According to theinvention, this transverse movement is used to activate, in particular,a valve slide of a hydraulic solenoid valve.

According to the invention, the magnet armature can also have twoarmature side faces which are cut from the longitudinal axis with anangle other than 90°, the two armature side faces being constructed in apreferred embodiment so as to be symmetrical with respect to a planeextending perpendicular to the longitudinal axis. In particular withthis construction of the two armature side faces, the components of theforce acting on the magnet armature which are generated as a result ofthe magnetic flux and extend in the direction of the longitudinal axiscancel each other out so that there is no additional loading in thelongitudinal direction of the armature tappet. This increases theoperational reliability of the pole according to the invention. Inaddition, a transverse force component whose absolute value is doubledin comparison with a single, obliquely arranged armature side face actson the magnet armature. This improves the efficiency of the poleaccording to the invention.

According to the invention, the coil core can have at least one or eventwo core side faces which are cut from the longitudinal axis at an angleother than 90°, it being possible for the two core side faces to beconstructed so as to be symmetrical with respect to a plane runningperpendicular to the longitudinal axis. Constructing the coil core insuch a way improves the guidance of the magnetic field lines in theinterior of the pole according to the invention, which increases itsefficiency. It is particularly advantageous here if in each case onearmature side face extends essentially parallel to a core side facelying opposite it because the course of the magnetic field lines in thepole according to the invention can then be configured particularlysatisfactorily. Furthermore, the behavior of a pole which is configuredin this way can be modeled and predicted particularly satisfactorily sothat in particular also linear activation processes and preciseadjustments are made possible.

In the configurations of the pole according to the invention describedabove, the designation “essentially parallel” with respect to theposition of armature side faces and core side faces means that in eachcase one core side face extends parallel to an armature side face in atleast one activation state of the magnet armature. It is not excludedhere that when the magnet armature is displaced one armature side faceassumes in each case a position with respect to a core side face inwhich they no longer extend parallel to one another. Such states canarise in particular when there are large displacements of an armaturetappet which is mounted on only one side.

Furthermore, it is possible to provide in the interrupted region of thecoil core a connecting region made of antimagnetic material whichconnects sections of the coil core to one another. This results in acompact and stable design of the coil core which is also sealed toprevent hydraulic fluid escaping.

In the interrupted region of the coil core, it is also possible toprovide a connecting region which has magnetizable material. As aresult, an additional air gap can be provided which, before the actualswitching of the magnet by an electrical coil in the region of themagnet armature, can be brought to saturation by an electrical coil inthe region of the magnet armature. This results in the armature beingadditionally acted on in its direction of movement even before themagnet armature according to the invention actually switches. In such astate, the magnet armature according to the invention is kept in astarting position from which it can be moved into its switched positionby increasing the current. Here, the force generated by the additionalair gap does not increase further because said air gap is preferablysaturated. However, the force generated by a working air gap between thepole and the magnet armature increases with the increase in the magneticfield density in the region of the pole. As soon as the force in theworking air gap is greater than the force in the additional air gap, themagnet armature moves in the direction of the force generated in theworking air gap. The force which is generated in the additional air gapdecreases with a very steep characteristic curve because the associatedair gap becomes larger and because at the same time the working air gapbecomes smaller. As a result, the force generated in the working air gapis available immediately, and to its full extent, for switching a magnetprovided with the pole according to the invention. Furthermore, thereare hardly any decelerations due to eddy currents if the main part ofthe magnetic field in the working air gap has already been built up by abiasing current.

The development according to the invention provides numerous advantages.For example, the current has to be increased only to a small extent toswitch the magnet according to the invention. At the same time, hardlyany eddy current decelerations occur during the switching, and a highswitching force is available just after the start of the stroke of themagnet armature. The armature according to the invention can be usedparticularly advantageously in conjunction with the particularadvantages of a swivel armature magnet which is obtained in such a way,namely those of a low armature mass and of negligible friction of thearmature within the pole, and by preventing an increase in mass as aresult of oil which is to be expelled through narrow drilled holes.

The pole according to the invention can be manufactured easily if thecoil core and/or the magnet armature are each constructed as anessentially cylindrical tubular section. Here, the magnet armature ispreferably constructed in such a way that it can be permanently attachedto a bar-shaped armature tappet while the coil core has athrough-opening which is constructed in such a way that the armaturetappet does not bear against the inside of the coil core even when thereare large displacements of the magnet armature.

If a first end of the armature tappet is permanently connected to afirst end of the coil core, when a displacement occurs the magnetarmature moves on an orbit about the mounting point of the armaturetappet on the coil core. A transverse movement of the magnet armaturewhich occurs here can then be transmitted particularly easily to, forexample, a valve slide of a hydraulic solenoid valve. There is alsoprovision here that a second end of the armature tappet projects beyonda second end of the coil core. In order to activate, for example, avalve slide, it is then sufficient to mount the coil core in a valvehousing and to bring the second end of the armature tappet into contactwith the valve slide.

The invention is also implemented in a magnet, in particular for ahydraulic solenoid valve, which has a pole which is configured accordingto the invention as described above, at least one electrical coil alsobeing provided in the region of the coil core.

The invention is also implemented in a magnet which has two electricalcoils which are preferably arranged coaxially with respect to oneanother. It is particularly advantageous here if use is made of a magnetpole in which a connecting region with magnetizable material is providedin the interrupted region of the coil core. With two such coils it isparticularly easily possible to achieve premagnetization, which permitsimproved operation with a second air gap.

In contrast to the above, or in addition thereto, it may be possible toapply not only two different operating voltages but also three differentoperating voltages to the electrical coil or coils. Here, it is possibleto switch, starting from a quiescent potential which constitutes thefirst operating voltage, via the second operating voltage into the thirdoperating voltage. The second operating voltage generates here thepremagnetization, while the third operating voltage constitutes theactual switching current of the magnet.

According to the invention, the magnet armature can, however, also bepremagnetized by means of a permanent magnet.

In addition, the invention also relates to a hydraulic solenoid valvewith at least one magnet according to the invention, the solenoid valvehaving a valve slide which can be activated by the armature tappet.

The swivel arm magnet according to the invention as described above isparticularly advantageous because it operates with low friction and as aresult has no wear, or only a small degree of wear. Furthermore, it ishighly responsive because it is not necessary to overcome any staticfriction in order to activate it. In particular in the construction withtwo obliquely extending working gaps which are symmetrical with respectto one another, the particular advantage is obtained that no resultingforce occurs in the axial direction of the armature tappet which is tobe bent. In addition, the magnet armature can be made particularlysmall, which improves the actuation characteristics of the magnetaccording to the invention. Furthermore, the magnet according to theinvention does not have any reduced oil mass so that no significantdynamic differences occur irrespective of whether there is oil or air inthe armature space. Finally, the magnet according to the invention is ofparticularly simple design.

The invention is also embodied in the form of a pole which has a magnetarmature in which the armature side faces intersect the longitudinalaxis at a right angle if at the same time the coil core has, in theregion of the magnet armature, at least one core side face which isintersected by the longitudinal axis at an angle other than 90°. Evenwith such a construction which is reversed in comparison with theconfigurations described above, the field lines in the air gap extendbetween the magnet armature and coil core in such a way that a forcecomponent which extends perpendicularly to the longitudinal axis anddeflects the magnet armature is produced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in the drawing by means of an exemplaryembodiment. In said drawing:

FIG. 1 shows a cross-section through a pole according to the invention,

FIG. 2 shows an enlarged detail of the illustration of the pole in FIG.1,

FIG. 3 shows a hydraulic proportional directional control valveaccording to the invention,

FIG. 4 shows a cross-section through a further pole according to theinvention,

FIG. 5 shows an enlarged detail of the illustration of the pole in FIG.4,

FIG. 6 shows a circuit diagram for the operation of the pole in FIG. 4,

FIG. 7 shows a further circuit diagram for the operation of the pole inFIG. 4,

FIG. 8 shows a circuit diagram for the operation of a further poleaccording to the invention,

FIG. 9 shows a schematic view of a further pole according to theinvention, and

FIG. 10 shows a circuit diagram for the operation of the pole in FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a cross-section through a pole 1. The pole 1 has a core 2with an essentially cylindrical outer shape on the outside of which anelectrical coil 3 is provided.

The coil 3 has an essentially pot-shaped coil housing 4 which isprovided, on its base side located to the right in FIG. 1, with a coreopening 5 which adjoins the outside of the core 2. On the side lyingopposite the core opening 5, the coil 3 is sealed with an annular washer6 whose inner circumference adjoins the core 2 and whose outercircumference adjoins the coil housing 4. A coil winding 7, which can besupplied with electrical energy by means of two terminals (not shown inthis view), is inserted into the space formed by the outside of the core2 and by the inner sides of the coil housing 4 and by the annular washer6.

The core 2 is divided into a first core section 8, which is located onthe left in FIG. 1, and into a second core section 9, which is locatedon the right in FIG. 1. The first core section 8 and the second coresection 9 are manufactured from magnetizable material and have a commonlongitudinal axis 10.

Here, the first core section 8 has a first end face 11 which is locatedto the left in FIG. 1 and which is produced as a cutting plane of aplane which extends perpendicularly to the longitudinal axis 10 andcomprises the first core section 8. On the end lying opposite the firstend face 11, the first core section 8 has a first core side face 12which is produced as a cutting plane of a plane which extends obliquelywith respect to the longitudinal axis 10 and comprises the first coresection 8. The first core section 8 is provided on its outer facelocated on the outside with a first pressure tube shoulder 13 to which apressure tube 14 made of antimagnetic material is attached.

The first core section 8 is also provided in the region of the first endface 11 with a tappet receptacle hole 15 which extends in the region ofthe longitudinal axis 10. The tappet receptacle hole 15 extends here inthe direction of the first core side face 12 to form a first tappetdrilled hole section 16. Here, an essentially rod-shaped armature tappet17 is inserted into the tappet receptacle hole 15 and secured there.

The second core section 9 has, at its end which is located to the rightin FIG. 1, a second end face 18 which is produced as a cutting plane ofa plane which extends perpendicularly to the longitudinal axis 10 andcomprises the second core section 9. At the end of the second coresection 9 lying opposite the first end face 18, a second core side face19 is constructed which is produced as a cutting face of a plane whichextends obliquely with respect to the longitudinal axis 10 and comprisesthe second core section 9. The second core side face 19 and the firstcore side face 12 are arranged symmetrically with respect to one anotherin a plane 20 of symmetry extending perpendicularly to the longitudinalaxis 10.

In the interior of the second core section 9, a second tappet drilledhole section 26 is also formed along the longitudinal axis 10, saidtappet drilled hole section 26 having a diameter which corresponds tothat of the first tappet drilled hole section 16. Here, the armaturetappet 17 extends through the second tappet drilled hole section 26 andemerges on the second end face 18. On the section of the armature tappet17 which emerges from the second core section 9, said armature tappet 17is of thickened construction to form an activation ball section 27.

On its outside, the second core section 9 is provided with acircumferential, second pressure tube shoulder 21 on which the pressuretube 14 is arranged. As a result, the second core section 9 is connectedvia the pressure tube 14 to the first core section 8, an armature space22 which is essentially in the shape of a trapezium in cross-sectionbeing constructed by the first core side face 12, the second core sideface 19 and the inside of the pressure tube 14.

A magnet armature 23 which is manufactured from magnetizable material isarranged in the armature space 22. The magnet armature 22 is essentiallyin the shape of a cylinder whose axis of symmetry extends parallel tothe longitudinal axis 10. The two end faces of the magnet armature 23extend obliquely with respect to the longitudinal axis 10, an end facebeing constructed as a first armature side face 24 which extendsessentially parallel to the first core side face 12. The other end faceof the magnet armature 23 is formed as a second armature side face 25which extends essentially parallel to the second core side face 19.Along the longitudinal axis 10, the magnet armature 23 is provided witha magnet armature drilled hole 26 through which the armature tappet 17extends. The magnet armature 23 is permanently mounted on the armaturetappet 17 and arranged in the armature space 22 in such a way that inthe quiescent state of the magnet armature 23 an air gap is formed onall sides between its outer surface and the inner surface of thearmature space 22.

Owing to the arrangement of the magnet armature 23 on the armaturetappet 17 mounted in the first core section 8, the activation ballsection 27 of the armature tappet 17 moves in a direction of movementindicated in FIG. 1 by two movement arrows 28 when the magnet armature23 moves in the armature space 22.

In order to illustrate the function of the pole 1, an enlarged detail ofthe illustration from FIG. 1 is used in FIG. 2, the enlarged detail inFIG. 2 being bounded by a contour line 29 which is shown in FIG. 1. Inaddition, for the purposes of illustration a magnetic field line 30which is shown by way of example in FIG. 1 is used, said field line 30representing the magnetic flux through the pole 1 when the coil winding7 is supplied with electrical energy. As is shown in FIG. 2, themagnetic field line 30 has a first field line section 31 which extendswithin the first core section 8, to be precise essentially parallel tothe longitudinal axis 10. Furthermore, the field line 30 has a secondfield line section 32 which extends within the magnet armature 23, to beprecise also essentially parallel to the longitudinal axis 10. Finally,the magnetic field line 30 has a third field line section 33 whichextends essentially parallel to the longitudinal axis 10 within thesecond core section 9.

In the air gaps between the magnet armature 23 and the first core sideface 12 or the second core side face 19, the field line 30 has a firsttransitional field line section 34 or a second transitional field linesection 35. The first transitional field line section 34 extends hereperpendicularly to the first core side face 12 and to the first armatureside face 24, while the second transitional field line section 35extends perpendicularly to the core side face 19 and to the secondarmature side face 25.

Forces F_(SL) which extend parallel to the first transitional field linesection 34 act in the air gap between the first core section 8 and themagnet armature 23 as a result of the magnetic flux through the core 2.In addition, forces F_(SR) which extend parallel to the secondtransitional field line section 35 act between the magnet armature 23and the second core side face. These forces F_(SL) and F_(SR) can bedecomposed into components which extend parallel to the longitudinalaxis 10 or perpendicular to the longitudinal axis 10. Here, there is aleft force triangle 36 and a right force triangle 37 which areillustrated by way of example in FIG. 2 together with a coordinatesystem 38. The two forces F_(SL) and F_(SR) are identical in terms ofabsolute value. However, they are different in terms of their respectivedirection. As can be seen in FIG. 2, their two components −F_(x) andF_(x) which extend in the x direction cancel one another out so that themagnet armature 23 is not acted upon by any force in the x direction.The two remaining components −F_(y) of the two forces F_(SL) and F_(SR)add together to form an overall force −2F_(y) which displaces the magnetarmature 23 in a direction opposite to the y direction.

As can be seen particularly well in FIG. 2, there is a relationshipbetween the angle which is enclosed between the first core side face 12,the second core side face 19, the first armature side face 24 or thesecond armature side face 25 and the longitudinal axis 10 on the onehand and the absolute values of the force components of the two forcesF_(SL)and F_(SR) acting in the direction of the y axis, on the other. Byvarying the above-mentioned angles and the size of the air gap in thearmature space 22, it is possible to react to different requirements interms of the required deflection of the activation ball section 27 atthe armature tappet 17. The smaller the cutting angle between thelongitudinal axis 10 and the first core side face 12, the second coreside face 19, the first armature side face 24 or the second armatureside face 25, the larger the proportion of the respective forcecomponents in the direction of the y axis.

FIG. 3 shows a solenoid valve 50 according to the invention incross-section.

The solenoid valve 50 has a valve housing 51 in which a valve pistondrilled hole 52 is provided with a valve piston 53 inserted therein.Hydraulic ducts 54 lead out of the valve piston drilled hole 52 to theoutside of the valve housing 51.

A pole drilled hole 55 which extends essentially perpendicularly to thevalve piston drilled hole 52 is constructed in the region of each end ofthe valve piston 53. In the outlet region of the pole drilled holes 55,they are expanded to form pole receptacle openings 56 into which in eachcase one pole 1 from FIG. 1 is inserted. Here, in each case the secondcore section 9 is pushed into the pole receptacle opening until theunderside of the coil housing 4 bears against the valve housing 4. Inthis state, in each case the activation ball sections 27 of the armaturetappets 17 touch the ends of the valve piston 53. A securing ring 57which is in each case fitted onto the first core section 8 secures thecoil 3 on the core 2 against slipping down.

During operation, the solenoid valve 50 behaves as follows. If the valvepiston 53 is to be pushed to the left in the illustration shown in FIG.3, the coil 7 of the pole 1 which is located to the right in FIG. 3 issupplied with electrical energy. The magnet armature 23 of the pole 1which is located to the right in FIG. 3 then moves to the left and thuspushes the tappet 17 and the activation ball section 27 to the left.Here, the activation ball section 27 of the pole 1 which is located tothe left in FIG. 3 is also pushed to the left until, owing to thebending of the armature tappet 17, it exerts an opposing force on thevalve piston 53 which has such a magnitude that a force equilibriumprevails. If this is desired, for example in the course of anadjustment, the pole 1 which is located to the left in FIG. 3 can alsosimultaneously be activated by supplying its coil winding 7 withelectrical energy.

After the interruption of the supply of electrical energy to the coilwindings 7, the armature tappets 17 and the valve piston 53 return tothe home position shown in FIG. 3.

FIG. 4 shows a further pole 60 according to the invention, whichcorresponds in its essential parts to the pole 1 according to theinvention in FIG. 1. Identical parts are therefore provided with thesame reference numerals.

The pole 60 has a pressure tube 61 which is essentially in the shape ofa hollow cylinder. The pressure tube 61 is divided here into a firstpressure tube section 62 made of magnetizable material, into a secondpressure tube section 63 made of antimagnetic material and into a thirdpressure tube section 64 made of magnetizable material.

The first pressure tube section 62 and the third pressure tube section64 are of such a length that the broader side of the magnet armature 23is just still located under the first pressure tube section 62 or underthe third pressure tube section 64.

In FIG. 4, in addition to the field line 30, a partial field line 65 isshown which starts from the first core section 8 and extends into thefirst pressure tube section 62, and from there enters the outer surfaceof the magnet armature 23. In the interior of the magnet armature 23,the partial field line 65 extends parallel to the second field linesection 32 and past the second pressure tube section 63 until it emergesfrom the magnet armature 23 in the region of the third pressure tubesection 64. There, the partial field line 65 enters the third pressuretube section 64 from where it runs into the second core section 9 andcloses the magnetic circuit again via the coil housing 4 and the annularwasher 6. The course of the partial field line 65 is illustrated in moredetail in FIG. 5.

FIG. 6 shows an electrical circuit 66 for operating the pole 60 fromFIG. 4. Only the coil 3 of the pole 60 is shown in FIG. 6. A voltage Ubcan be applied to the coil 3 via a first switch 67. A diode 68 is alsoarranged in the circuit which is closed by the first switch 67.

The electrical circuit 66 also has a second switch 68 via which a secondoperating voltage Ua can be applied to the terminals of the coil 3.Here, the second operating voltage Ua is higher than the first operatingvoltage Ub.

During operation, the magnet pole 60 which is wired according to FIG. 6behaves as follows. In a state before switching occurs, the first switch67 is in the closed state. In this state, there is saturation in theregion of the air gaps between the first pressure tube section 62 andthe magnet armature 23, and between the third pressure tube section 64and the magnet armature 23, respectively. In order to switch the pole60, the second switch 69 is activated so that the coil 3 is alsosupplied by the operating voltage Ua. In this state, the force generatedin the working gap between the first core section 8, the magnet armature23 and the second core section 9 is of such a magnitude that the magnetarmature 23 is pulled downward in the view shown in FIG. 4. As a result,in each case the air gap between the magnet armature 23 and the firstpressure tube section 62 or the second pressure tube section 63 isincreased so that the greater part of the flux of the magnetic field isdisplaced into the part of the working air gap. As a result, there is arapid switching process of the pole 60 according to the invention.

FIG. 7 shows a further schematic circuit diagram relating to theoperation of the pole 60, according to the invention. According to FIG.7, a single voltage source Ub is sufficient for this, it being possibleto apply to the coil 3 a voltage, reduced by a series resistor 70, viathe first switch 67 and the series resistor 70. The second switch 69 isconnected in parallel with the series resistor 70, the second switch 69bypassing the series resistor 70 when activation occurs. This ensuresthat the coil 3 can have a total of three different operating voltagesapplied to it depending on the position of the first switch 67 and ofthe second switch 69.

FIG. 8 shows a circuit diagram relating to the operation of a pole (notshown in this view) which has a first coil 71 and a second coil 72.Here, the first coil 71 is used for pole premagnetization according tothe invention, while the second coil 72 is used to connect through thepole. The operating voltage Ub is applied to the first coil 71 via thefirst switch 67. The operating voltage Ub is applied to the second coil72 by means of the second switch 69.

FIGS. 9 and 10 show a further pole 73 according to the invention, ofwhich this view shows only a magnet armature 74, a pressure tube 75, acoil housing 76, a coil 77 and a permanent magnet 78 which is arrangedin the region of the coil 77.

When the pole 73 is operating, the magnet armature 74 is premagnetizedby the permanent magnet 78. In order to activate the pole 73, a firstoperating voltage Ua and a second operating voltage Ub can be applied tothe coil 77, which can be seen particularly well in FIG. 9. The voltagesUa and Ub each have a reversed polarity so that the polarity of the coil77 can be reversed using switches 79 in order to switch the permanentmagnet 78 on or off.

I claim:
 1. An electromagnet, for actuating a hydraulic solenoid valve(50), having a coil core (8, 9) of an electrical coil in a region of thecoil core, which coil core is made of magnetizable material and extendsalong a longitudinal axis (10), the electromagnet also having thefollowing features: an armature tappet (17) which extends essentiallyparallel to said longitudinal axis (10) is provided in a tappet opening(16) which extends in the interior of the coil core (8, 9) at least onemagnet armature (23) is provided on the armature tappet (17), saidmagnet armature (23) having at least one armature side face (24, 25)which cuts through the longitudinal axis (10) at an angle other than90°, and the coil core (8, 9) is interrupted in a region of the magnetarmature (23).
 2. The electromagnet as claimed in claim 1, wherein themagnet armature has two armature side faces (24, 25) which are cut fromthe longitudinal axis (10) at an angle other than 90°.
 3. Theelectromagnet as claimed in claim 2, wherein the two armature side faces(24, 25) are constructed so as to be symmetrical with respect to a plane(20) which extends perpendicularly to the longitudinal axis (10).
 4. Theelectromagnet as claimed in claim 1, wherein the coil core (8, 9) has atleast one core side face (12, 19) which cuts through longitudinal axis(10) at an angle other than 90°.
 5. The electromagnet as claimed inclaim 4, wherein the coil core (8, 9) has two core side faces (12, 19)which are cut through the longitudinal axis (10) at an angle other than90°.
 6. The electromagnet as claimed in claim 5, wherein the two coreside faces (12, 19) are constructed so as to be symmetrical with respectto a plane (20) which extends perpendicularly to the longitudinal axis(10).
 7. The electromagnet as claimed in claim 4, wherein in each caseone armature side face (24, 25) extends essentially parallel to, in eachcase, one core side face (12, 19).
 8. The electromagnet as claimed inclaim 1, wherein a connecting region (14) which has antimagneticmaterial is provided in the interrupted region of the coil core (8, 9).9. The electromagnet as claimed in claim 8, wherein a connecting regionwhich has magnetizable material (62, 64) is provided in the interruptedregion of the coil core (8, 9).
 10. The electromagnet as claimed inclaim 8, wherein the connecting region (14) has a tubular shape andconnects interrupted sections of the coil core to one another.
 11. Theelectromagnet as claimed in claim 1, wherein a first end of the armaturetappet (17) is permanently connected to a first end (11) of the coilcore (8, 9).
 12. The electromagnet as claimed in claim 11, wherein asecond end of the armature tappet (17) projects beyond a second end (18)of the coil core (8, 9).
 13. The electromagnet as claimed in claim 1,wherein two electrical coils which are arranged coaxially with respectto one another are provided.
 14. The electromagnet as claimed in claim1, wherein at least three different operating voltages are applicable tothe electrical coil (3) or electrical coils.
 15. The electromagnet asclaimed in 1, further comprising a permanent magnet (78) arranged in theregion of the coil core.